Cathode-ray tube



J. M. CAGE CATHODE-RAY TUBE Oct. 2, 1951 Filed Nov. 19, 1948 Jbl/,v MQ65 Y w 7M, ATTORNEYS a Patented Oct. 2, 1951 UNITED .STATES PATENTOFFICE 2,569,654 cATHoDE-RAY TUBE John M. cage, Montclair, N. J.

Application November 19, 1948, Serial No. 60,868

(o1. 31a-s3) 16 Claims.

This invention relates to image reproducing tubes of the cathode raytype that are useful for the reproduction of televised images and forother purposes.

One object of my invention is a new and improved means for shielding theelectron beam in cathode ray tubes.

Another object of my invention is a new and improved cathode ray tubewherein the high potential elements are effectively insulated within thetube so that extremely high potentials can be applied without the dangerof arc-over either through the glass or through the tube.

Another object of the invention is a new and improved tube of thecharacter set forth wherein the tube wall or envelope can be maintainedat a ground or other relatively low potential as compared with theaccelerating potential.

Another object of the invention is to provide a relatively small cathoderay tube capable of operating at very high potentials.

Another object of the invention is a newl and improved cathode ray tubeof the character set forth wherein greatly improved operation andpicture brightness is obtained.

Another object is a cathode ray tube wherein contamination of the vacuumis effectively prevented during the operation of the tube.

Another object of the invention is to provide means within the tube todefine the picture size and shape that is to be projected.

Still another object of the invention is a new and improved cathode raytube.

The above and other objects of the invention will become more apparentin the following description and the accompanying drawings.

In the drawingsf Fig. l is a diagrammatic view of one embodiment of theinvention;

Fig. 2 is a cross-sectional view of another embodiment thereof;

Fig. 3 is a cross-sectional view of the embodiment of Fig. 2 taken alongthe line 3-3 thereof; and

Fig. 4 is another embodiment of the invention.

In Fig. 1 I have diagrammatically illustrated one form of the inventionas applied to a. projection type television reproducing tube. The outerenvelope I of the tube is preferably formed at least in part of metalwith a window 2 of glass or other transparent material. At the base orrighthand end 3 of the tube is an electron gun 4 of conventionalcharacter for generating and controlling the electron beam. The highvoltage elements, namely the image screen 5 and the second anode 6 areheld in spaced relationship within the tube by a member 1 which extendsto a point spaced from the window 2 on one end and from the electron gun4 on the other end. The screen 5 is positioned within and a shortdistance from the end of the member 1 to provide a light shield part 'l'and prevent reflected light from quenching the darker parts of the imageformed on the screen 1. For this purpose the inner surface of the shield'l' is preferably of a black mat finish.

The member 1 may be made in whole or in part of a conductive material ormay be of a nonconductive material with a partial or complete conductivecoating thereon, depending on the particular purpose for which the tubeis to be used The high or accelerating voltage is connected to themember 1 by the conductor 8 centrally disposed in the insulator 9.

By fabricating the outer envelope l of metal and providing suitableinsulating supports between it and the innermember 1, the envelope canbe retained at ground or near ground potential and thereby insuremaximum safety for personnel using or servicing the equipment and alsoprevent external electric fields from affecting the tube operation.Moreover, any harmful rays generated within the tube can be blocked bythe metal envelope.

Internal or external deflecting and focusing means may be used forcontrolling the beam after acceleration thereof, depending on the tubestructure. These are usually located after the second anode as, forexample, at the place indicated by external coils denoted by the numerall I. These coils may accomplish the l'lnal step of focusing the beam onthe screen 'l and constitute the deflecting means for causing the beamto scan the screen in any desired manner.

The embodiment of my invention shown in Fig. 2 of the drawings overcomescertain limitations of conventional structures known to me and includesan outer metal envelope having a tubular glass neck portion extendingtherefrom to house the gun and focusing electrodes. The tubular neckportion has been formed of glass in order to enable the use ofconventional external magnetic focusing and deflecting means of the typeshown in Fig. 1 for the control of the electron beam. The tubular neckpart of the tube can obviously be fabricated of metal should it bedesirable, for example, to use focusing and deecting means containedwholly within the tube.

More particularly the outer metal envelope I0 is preferably formed intwo parts I2 and I4 that may be sweated or otherwise suitably fastenedtogether substantially as indicated at I6. By separating the metallichousing in this way, the assemblyv as well as the fabrication of thetube ycomponents and the metallic shells is greatly simplified as willbecome apparent.

` The electron'gun illustrated diagrammatically at I8 and 20 is housedin the neck-like part. 24 of the tube and supported by the closed endthereof located within the socket or base of the tube 22. The tubular orneck part 24 is illustrated as being of glass and is sealed in anysuitable manner to the metallic shell I2 as shown at 26. It may,however, be desirable in certain instances to fabricate the neck part 24also of metaLand in that case the neck 24 and the envelope part I2 canbe made of one piece.

In cathode ray tubes the electron beam is produced and controlled by theelectron gun, whereupon it then is greatly accelerated by the secondanode disposed just ahead of the gun and proceeds to the other end ofthe tube to strike and illuminate a screen. The second anode and screenara therefore maintained at a very high potential which in projectiontype tubes may be as high as 30,000 or 40,000 volts and even higher. Toprevent the accumulation of charges on the envelope walls they aregenerally coated with aquadag or other similar conductive coating andcharged to the same or similar potential as the second anode and screen.With this arrangement it has been found that damaging electricaldischarges frequently occur through the glass envelope itself or overthe supports holding the second anode and other parts of the electrongun in alinement and for supporting them concentrically inside thecylindrical section 24 of the tube.

This new and improved tube overcomes this difliculty through the use ofa new and improved structure adapted to hold the high voltage elementsof the tube in spaced relationship to the outer tube envelopes. For thispurpose I have provided a unitary structure 28 of glass or othersuitable insulating material arranged to hold the high voltage elementsabove referred to in the desired relationship one to the other and tothe electron gun.

More particularly the lunitary structure 28 consists of a relativelylarge cylindrical portion 30 tapered at the rear thereof to form a long,narrow cylindrical part 32 adapted to fit in and be spaced from theneck-.like part 24 of the tube. Surrounding the structure 28 is anoutwardly extending flange 34 of insulating material such as glass orthe like for supporting the structure 28 within the envelope. Although Ihave illustrated this flange as extending around the larger part 30 ofthe member 28, it may take the form of a plurality of individualprojections arranged in line about the member or staggered over thesurface thereof.

In the illustrated embodiment the flange 34 cooperates with a pair ofsurrounding metallic brackets 36 and 38 sweated or welded to theenvelope part I2 to hold the member 28 in proper alinement with theenvelope I0. In assembly of the tube, bracket 36 is first positioned inthe shell part I2 and suitably fastened thereto. The member 28 is theninserted in the tube part I2 until the flange 34 seats flush on the ring36, which automatically alines it with the outer envelope parts and theelectron gun, whereupon the second ring on bracket 38 can be fastened inplace as shown to rigidly hold the member 28 in place..

On the end of the smaller cylindrical part 32 of the member 28 I havesecured the second or accelerating anode 40 so that whenthe member 28 ismounted in the outer envelope it will bc properly alined with and spacedfrom the other gun elements I8 and 20. The anode 40 is held -within thetubular part 32 by a plurality of wires or strips 42, each fastened tothe anode and extending forward through the tubular part 32. The endpart of each wire is bent outwardly to engage the conical part of member28. A suit able flange or stop 44 may be provided on the anode 48 tolimit its forward movement relative to the tubular part 32.

The reproducing screen 46 for interrupting the electron beam is fastenedto the large end of the member 28 and has a suitable layer ofphosphorous and aluminum on the inner side thereof. On the other orouter side of the screen 48 I have positioned a mask or mat 50 (Figs. 2and 3)- having a rectangular opening 52 therein through which thereproduced image is visible. By employing a mat of this character, thesize of the picture can be pre-adjusted to eliminate any edge distortionand produce a well defined projection. Moreover, the screen 48 is fiatand with proper control of the scanning means to correct for the lack ofscreen curvature, a very much improved picture is obtained.

To prevent the accumulation of a charge on the member 28, I prefer tocoat the inside of the larger part 30 with'a suitable conductive coating54 of silver or the like extending from the screen 48 to a point spacedfrom the rods .or wires 62 so as to prevent any electrical connectionbetween the forward ends of the wires. One of thc wires 42, however, isconnected to the coating 54 at 56 and the coating is connected to thescreen 48 by a suitable conductive coating or jumper 58. The member 28instead of beil q formed of glass having conductive coatings on theinside thereof, may be formed in whole or in part of a suitableconductive material and thereby avoid the necessity of conductivecoatings on certain parts thereof.

The high voltage supply for the accelerating anode 40, screen 48 and theconductive coating 54 is brought into the tube through a recessedinsulator 60 welded to the edge of an opening 52 in the metallic housingpart I2. The insulator 60 is preferably cylindrical in shape and has auinner cylindrical part 64 closed at its bottom end and joined on itsupper side to the edge of ihr: outer cylinder. A high voltage conductor66 extends through the closed end of the inner cylinder 64 and isconnected on its inner end to a short pigtail 68 which in turn extendsthrough the member 28 and is connectedto the coating 54 at 18.

The metallic end portion I4 of the tube envelope is tapered inwardlytoward the left as viewed in Fig. 1 to form a short cylindrical sectionI4' which terminates in a somewhat smaller opening 12. Within thisopening I2 is welded a glass window 'I4 having a diameter sufficient topermit the entire picture defined by the aperture 52 to be projectedonto an external screen. A projection lens I3 is used to focus thereproduced image on the external screen and is sldably mounted within ametallic cylinder 16 arranged to forcibly fit the cylindrical part I4'and be wholly supported thereby. This method of mounting the projectionlens insures accurate alinement of the lens within the screen 48 and anymovement o! "e tube would not cause it to be thrown out of line with itsoptical system. 'If desired, the lens supporting cylinder 16 may besweated or other= wise secureb' fastened in place on the envelopesection |4-.

To prevent reflected light from quenching the image formed on the`screen 48, a light shield 49 may be placed in front of the screen andheld in ppsition in any suitable manner as by the enlargedfcylindricalpart 5| engaging the outer surface of the member 28. This shield shouldpreferably have a black mat finish at least on the inside thereof.

Fig. 4` illustrates another embodiment of the invention wherein theouter envelope is formed of glass'or other suitable material. Theinternal structure of the tube is similar to that shown in Fig, 2 andlike parts in each ligure have been formed and designated by likenumerals.

In this embodiment I prefer to form the outer envelope i0 of threeindividual-sections, namely, IIB, H2. andv ||4. The section ||0 includesa tapered neck-like part ||6 which is similar to the neck-like portion24 of Fig. 2 and is tapered outwardly toward the left to meet and abutthe cylindrical sectionv ||2. The inner member 28 supporting the screen48.111 the second anode 40 is positioned in theV tube with its flange 34interposed between the meeting surfaces of the tube envelope` parts |||land H2 as illustrated at HB and these parts are glass-welded together toform a substantially unitary structure. Upon the welding of the pigtaillead 88. which is fastened to` the coating 54 at l0 to the leading inconductor 66, the front section H4 may then be weldedin place asindicated at |2|l.- Although I have indicated the front section I4 ofthe envelope as having a short cylindrical part ||4', this part of thetube could obviously be made in any desired manner. This front sectionof the envelope'isclosed by a curved window 14' to modify thelightpassing therethrough, it being understood, However, that this window 14can be formed as an integral part of the front envelope section I4. YThewindow 'i4' is particularly usefulin projection tubes since itconstitutes one of the; optical elements of a projection lens, the other.elements being indicated diagrammatically at 13'.; This structureeliminates one thickness of glass through which the image is to beprojected and the attendant light losses. 4

I haue also illustrated in-this embodiment of the' invention a new andimproved getter to inactivate contaminating gases within the tube afterit has, been evacuated. For this purpose a piece of gel-,tering materialI 22 is mounted on suitable supporting wires |24 and |26 disposed withinthe cylindrical opening |28 in the insulator 60. The mounting of thegetter in this way will not materially affect the long linkage pathobtained by use of the insulating structure 60 and will put the getterin position where it can be easily fired The tube structure which I haveillustrated in the drawings is particularly useful in high v oltageapplications where it is desired to project televised images, since allof the high voltage elements are completely and fully insulated from thesurrounding envelope. In the embodiment of Fig. 2 the metallic envelopecan be grounded so as to prevent the formation of a charge thereon thatmay endanger persons working on or wiring the equipment,V andfurthermore, the shell can be made of a metal that will effectivelyprevent the transmission of the harmful rays that may be generatedwithin the tube by reason of the employment of very high voltages.Moreover, the metal shell will prevent external magnetic ileldsfromaffecting the electron beam in any way. Where deecting means areincorporated wholly within the tube envelope, as previously described,the entire outer envelope can be formed of metal and thereby provideeven more effective shielding.

This application is a continuation in part of my copending applicationfor U. S. patent, Serial No. 46,585. filed August 28, 1948, for CathodeRay Tube."

I claim:

l. A cathode ray tube comprising an outer envelope having a largecylindrical section closed on one end by a transparent window and asmall by an external source of electro-magnetic energy.

In order to insure the inactivation of all of the residual gases withinthe tube I provide an opening |33 in the member 28 just below theposition of the getter |22 in the high voltage terminal i0. In this waythe vapors produced by the getter |22 in firing will not only pervadethe space surrounding the member 28 but part of them will be directedinto the opening in member 28 to completely and effectively inactivateharmful residual gases. It is apparent that this method of gettering isequally applicable to the tube illustrated in Fis. 2.

cylindrical neck-like part extending therefrom, an electron gun in saidneck-like part to generate and direct an electron beam along the axis ofthe envelope, a member within the envelope and in spaced relation to thewalls thereof, said member carrying on one end thereof an acceleratinganode in alinement with the gun and on its other end a reproducingscreen spaced fromthe window and adapted to interrupt the beam fortheformation of images thereon.

2. A cathode ray-l tube according to claim l whereinsaid outer envelopeis formed at least in part of metal.

3. In a cathode ray tube, a high voltage entrance insulator extendingfrom the surface of the tube and having inner and outer walls definingan intermediate opening communicating with the inside of the tube, andgettering means disposed in said opening.

4. A cathode ray tube comprising an outer envelope, a hollow walledinsulator extending from ment of a high voltage lead-in wire, highvoltage elements within the tube including a second anode and screen, aunitary member centrally of the envelope for holding the high voltageelements, gettering means disposed in the insulator f gettering the tubeand an opening in said unitary member and in line with the getter toallow vapors produced by the getter when it is fired to pass into saidunitary member.

5. A cathode ray tube including an electron gun comprising an outerenvelope, a unitary member of smaller diameter than the envelope axiallyaiined therein, an anode on one end of said member in spacedrelationship to the electron gun, a screen on the other end of saidmember. and shielding means on the walls of said member for preventingthe accumulation of an electrostatic charge on the walls thereof.

6. A cathode ray tube of the character set forth in claim 5 wherein saidunitary member is formed of a conductive material.

7. A cathode ray tube according to claim 5 wherein said shielding meanscomprises a plurality of individual wires in spaced relationship andsponsive screen in said envelope and spaced from l the window, and acylindrical member positioned between the screen and the window toprevent direct or reflected light from quenching the darker parts of animage formed on the screen.

9. In a cathode ray tube having a gun structure enclosed within theevacuated tube envelope comprising means for controlling and focusingthe beam produced by the gun and a second anode for accelerating thebeam including a plurality of individual elongated conductive elementsextending from said anode in the direction of movement of the beam,unitary means in said envelope for supporting the second anode andconductive elements and a screen in said tube mounted on the end of saidunitary member for the reproduction of images thereon.

10. In a cathode ray tube having an electron gun enclosed within theevacuated tube envelope comprising means for controlling and focusingthe beam, a second anode for accelerating the beam including a pluralityof individual elongated conductive elements extending from said anode inthe direction of movement of the beam, an electron responsive screen insaid envelope spaced from the wall thereof. said envelope having awindow therein in alinement with said screen and adapted to transmitlight patterns produced by said screen, said window being curved tomodify the light emitted by the screen and passing through the window.

11. A cathode ray tube having an electron gun enclosed within theevacuated tube envelope comprising means for controlling and focusingthe beam, a second anode for accelerating the beam including a pluralityof wirelike elements extending from the anode in the direction ofmovement of the beam, said elements being spaced about the beam andconnected one to the other and to the second anode, a screen within saidenvelope to interrupt the electron beam for the reproduction of imagesformed thereby, and individual means within the tube for supporting thescreen and the second anode including the wirelike elements.

12. In a cathode ray tube according to claim 11 wherein said elementsare electrically connected together at the second anode and are spacedsubstantially uniformly about the beam.

13. The combination with a cathode ray tube as set forth in claim 11 ofa window in said tubp envelope to transmit light produced by th'escreen, said window having diierentially curved surfaces to modify thelight passing therethrough.

14. In an image reproducing tube, an electron gun for producing anelectron beam, an anode for accelerating said beam including a pluralityot spaced insulated elements extending from the anode in a direction ofmovement of the beam. said elements surrounding and providing anelectrostatic shield for the beam, an electron responsive screen forintercepting the beam, and means for supporting the second anode, thespaced elements and the screen in alinement one with the others and withthe electron gun.

15. The combination with an image reproducing 'tube as set forth inclaim 14 of a window in said tube for transmitting the light produced bythe screen, said window being curved to provide parts having differentthicknesses to modify the image passing therethrough.

16. A cathode ray tube comprising an outer envelope, an electron gun inone end of said envelope and a transparent window in the other endthereof, an internal tubular member withinA said envelope and extendingfrom the gun to a point spaced from the window, said member being atleast in part conductive, a second accelerating anode on the end ot saidmember adjacent the gun and a screen supported within the other end ofsaid member, said screen being spaced a greater distance from the windowthan the adjacent end of said member.

JOHN M. CAGE.

REFERENCES CITED The following references are of record in the ille ofthis patent:v

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